Orders from your marketplace store(s) can be viewed by selecting "Orders --> All Orders" from the left-hand menu.
This will take you to the "Orders" landing page.
From here you can search by order number/customer email, or use the filters to find a particular order, or types of orders (e.g. orders with a status of "Shipped").
After locating an order, simply click on the "Order Number" value to see the full order details